An engine includes: a piston including a cavity; a cylinder head configured so as to form a combustion chamber having a pent roof shape; a fuel injection valve configured to inject fuel from a second half of a compression stroke until a first half of an expansion stroke; and a spark plug arranged at a position corresponding to an upper side of the cavity. Injection openings which are arranged in a circumferential direction surrounding a longitudinal axis of the valve and through each of which the fuel is injected in a direction inclined relative to the longitudinal axis by a predetermined angle is formed such that when a height of a ceiling of the combustion chamber at a position corresponding to an edge end portion of the cavity in an injection direction of the injection opening is large, the injection angle of the injection opening is large.

When it is determined that the initial combustion is unstable, the engine speed is forcibly increased. When the engine speed is forcibly increased, fluidity in the cylinder increases. When the fluidity in the cylinder rises, homogeneity of the homogeneous air-fuel mixture is improved. Therefore, it is possible to enlarge the flame kernel. When the flame kernel is enlarged, the initial flame resulting from the flame kernel is also enlarged. Then, the initial flame becomes easy to involve the closest fuel spray thereby the initial combustion can be stabilized.

An improved air-cooled aviation engine includes a compact combustion chamber having an intake valve opening, an exhaust valve opening, and a generally elliptical shape. The elliptical shape has a major axis and a minor axis, with the major axis intersecting both the intake valve opening and the exhaust valve opening. In some examples, the major axis is the same length or shorter than a diameter of a cylinder bore of the engine, and the minor axis is smaller than the major axis. Combustion is thus constrained to a smaller area than that of the cylinder bore.

An object of the invention is to form a highly homogeneous air-fuel mixture which is not influenced by an engine rotation speed. Therefore, the invention provides a fuel injection control device including a cylinder, a first injector disposed at an upper portion of the cylinder in the axial direction and a center portion thereof in the radial direction, an intake valve disposed at an upper portion of the cylinder in the axial direction and an outer portion thereof in the radial direction in relation to the first fuel injection device, and a second injector supplying fuel from an upper portion of the cylinder in the axial direction and at least an outer portion in the radial direction in relation to the intake valve, in which a rotation speed of the engine is high, a fuel supply amount ratio of the first injector with respect to the second injector is controlled to be larger than that of a case where the rotation speed is low.

An engine includes: a piston including a cavity; a cylinder head configured to form a combustion chamber having a pent roof shape; a fuel injection valve configured to inject fuel from a second half of a compression stroke until a first half of an expansion stroke; and a spark plug arranged at a position corresponding to an upper side of the cavity. Injection openings are arranged in a circumferential direction surrounding a longitudinal axis of the valve. The combustion chamber at a compression top dead center is divided into a plurality of fuel injection regions, located in respective injection directions of the injection openings, by vertical surfaces extending radially from the longitudinal axis through a middle between adjacent injection openings. When a volume of the fuel injection region located in the injection direction of the injection opening is large, an opening area of the injection opening is large.

The present invention relates to a combustion chamber structure of an engine configured to inject fuel in a predetermined operation range in a period from a second half of a compression stroke until a first half of an expansion stroke to perform ignition after a compression top dead center. The combustion chamber structure includes: a piston including a cavity; a fuel injection valve provided at a middle portion of the piston; and a spark plug provided at a radially outer side of the middle portion of the piston and an upper side of the cavity. The cavity is formed by a curved surface having curvature that becomes larger as the curved surface extends toward the radially outer side. A tangential direction of an edge end portion of the curved surface intersects with a combustion chamber ceiling radially outward of the spark plug.

The present invention relates to an internal-combustion engine comprising a combustion chamber provided with a single intake valve (2), a single exhaust valve (3), two plugs (4a, 4b) and a fuel injector (5). Furthermore, the combustion chamber comprises means for forming an aerodynamic swirling motion structure of the intake gas in the combustion chamber. Besides, fuel injector (5) is oriented so as to inject the fuel into the central area of the combustion chamber in the direction of the aerodynamic swirling motion structure.

The present invention relates to a combustion chamber of a combustion engine. The combustion chamber comprises a single intake valve (2), a single exhaust valve (3), a fuel injector (5) and two plugs (4). According to the invention, the combustion chamber is substantially elliptical (6) and the components of the combustion chamber are arranged as follows: valves (2, 3) are located at the ends of the major axis (8) of ellipse (6), plugs (4) are located close to the minor axis (9) of ellipse (6), fuel injector (5) is located on the periphery of ellipse (6) between intake valve (2) and a plug (4).

The present invention relates to an internal-combustion engine comprising at least two cylinders wherein a piston in connection with a combustion chamber moves. Said combustion chamber comprises a single intake valve (SA), a single exhaust valve (SE), a single fuel injector (ID), two spark plugs (Al) and means for creating a swumble flow in said chamber.

The present disclosure relates to an internal combustion engine, comprising: at least one cylinder; two charge-exchange ports per cylinder, a first charge-exchange port being an inlet port, and a second charge-exchange port being an outlet port; and one spark plug and one prechamber spark plug per each cylinder.